1. Field of the Invention
The invention relates to light weight aircraft. More particularly, the invention is related to a system and method for eliminating or substantially reducing wing peak loads and/or damage in a light weight aircraft.
2. Background Art
Large, low wing-loading aircraft, in particular solar powered aircraft, can have very high structural loads in gusts when operating at low altitude. They can also have structural dynamics problems, such as the one that led to the loss of the Helios aircraft. Wing loading, as those of ordinary skill in the art know, is the loaded weight of the aircraft divided by the area of the wing. It is broadly reflective of the aircraft's lift-to-mass ratio, which affects its rate of climb, load-carrying ability, and turn performance.
Typical aircraft wing loadings range from about 10 lb/ft2 (100 kg/m2) for general aviation aircraft, to 80 to 120 lb/ft2 (390 to 585 kg/m2) for high-speed designs like modern fighter aircraft. The critical limit for bird flight is about 5 lb/ft2 (25 kg/m2). A low wing loading aircraft, therefore, is typically in the range of about 1 lb/ft2 to about 20 lb/ft2.
Wing loading has an effect on an aircraft's climb rate. A lighter loaded wing will have a superior rate of climb compared to a heavier loaded wing as less airspeed is required to generate the additional lift to increase altitude. A lightly loaded wing has a more efficient cruising performance because less power is required to maintain lift for level flight.
While the low power requirements of a light wing loading airplane are desirable for high altitude, long endurance aircraft, the resulting low flight speed means that the aircraft can be subjected to very large gust loads when it is flying in dense air at low altitudes. In particular, the speed of the wind gusts may be greater than the airspeed of the airplane. Also, these aircraft can be quite large, and may even have a wingspan larger than the cell size of the low altitude turbulence. This can produce uneven loads on the wing, and require especially strong wing spars to withstand the loads. Making the spars stronger to withstand the additional wind gust loads adds weight to what would otherwise be a very light weight, highly efficient airplane
Thus, a need exists for a wing structure on a light weight aircraft that can handle relatively large, and perhaps localized, gusts with respect to the wing area, without permanent bending or damage to the wing structure.